Cooling heat-generating components, such as integrated circuit devices, is often desirable to ensure their proper operation and to extend their useful life. A trend in contemporary circuit design is to provide multiple heat-generating components on a printed circuit board. A consequence of providing multiple heat-generating components on a printed circuit board, which may include integrated circuit devices operating at relatively high speeds, is substantial heat production that may be detrimental to the operation and life of those components. Conventionally, heat sinks are used to transfer heat from the heat-generating components to an area where the heat can be dissipated, such as the atmosphere. Alternatively, or in addition, adequate forced ventilation is provided to remove the heat from the heat sink.
Some conventional approaches to thermal management of packaged electronic devices require the mating of individual heat sinks with individual components. The use of individual heat sinks can be expensive and the associated installation may be labor intensive. Further, as more heat-generating components are provided onto ever-smaller printed circuit boards, each heat sink must be accurately aligned with its neighbor to ensure proper function.
Other conventional heat sinks are also adapted for cooling a multiplicity of heat-generating components. Variations in the manufacturing and assembly processes, however, frequently result in seemingly identical components that have top attachment surfaces, over which the heat sink is provided, at slightly different heights. Possible sources of height differences include, for example, variances in the size of solder balls used to attach components to a substrate, variances in bends of leads used for component attachment, variances in thickness of solder connections, and dimensional variances in other attachment features used for this purpose. Moreover, different components having top attachment surfaces located at different heights may often be provided on the same printed circuit board. In a conventional configuration resulting in different component height, highly compressible thermally conductive gap pads or gap filler materials may be used to fill gaps between the bottom of the heat sink and the top surfaces of the components to be cooled, enabling effective thermal transfer to the heat sink from the shorter components. Gap pads may be attached between the heat sink and the components by thermally conductive epoxy or by mechanical means, such as clamps or fasteners. Alternatively, the heat sink may be configured to deform in response to an applied downward force to contact the top surfaces of components and be attached thereto. Further, gap filler material, such as a thermal interface material (TIM), may also be provided to fill gaps between the heat sink and the components. Conventionally, TIMs are able only to fill relatively thin gaps because a thicker layer of TIM may not provide adequate heat dissipation. Any of these configurations, however, may result in inadequate heat transfer from components due to suboptimal, or failed, thermal attachments or may introduce unacceptable stress on thicker components having top surfaces most out of plane with the top surfaces of the remainder of the components.